HANGZHOU, July 31 -- A subway that is under construction in Hangzhou, capital city of east China's Zhejiang Province, flooded on Thursday.

Water was found leaking into the section between Jiangjin Road Station and Citizen Center Station on Subway Line 4 in the morning.

When Hangzhou Metro workers went to investigate and carry out repairs, they found that the cofferdam of Xintang River had collapsed causing water to flood into Citizen Center station.

A cofferdam is a temporary watertight structure used in construction projects that would normally be submerged in water, creating a dry work environment.

Workers on site were evacuated immediately. Repair work is under way and river water has stopped leaking into the station. No casualties have been reported.

According to the Hangzhou Metro website, only Subway Line 1 is in operation. The 20.8-kilometers Subway Line 4 will be put into use next year.